Double-walled vessel



FIG. 1 is an oblique view of the claimed design seen from a first perspective;

FIG. 2 is an side view of the claimed design;

FIG. 3 is a top view of the claimed design; and,

FIG. 4 is a bottom view of the claimed design. 

CLAIM The ornamental design for a double-walled vessel, as shown and described. 